The American Gas Association has published an American National Standard and addenda thereto for acceptable performance for quick-disconnect devices for use with gas fuel at relatively low pressures. Standard Z21.41, entitled Quick-Disconnect Devices For Use With Gas Fuel, was approved on Jan. 16, 1989 by the American National Standards Institute. The Standard sets forth at page 1, among other requirements, that the quick-disconnect devices "shall be equipped with automatic means to shut off the gas when the devices are disconnected." Under the Standard, the mating parts of the quick-disconnect device can be disconnected by manual engagement or by providing opposing separating forces on the coupling members.
The quick-disconnect devices described in the Standard are used in a variety of applications. For example, most restaurants, and virtually all fast food restaurants, use a quick-disconnect coupling in connection with a deep fryer that is heated with natural gas fuel. The deep fryer normally has a hose for receiving fuel that is connected by a quick-disconnect coupling to a source of the fuel.
Problems have arisen in the use of gas fuel for heating deep fryers. Deep fryers heat flammable oils to high temperatures and are prone to frequent fires. Many quick-disconnect couplings that shut off the flow of gas when disconnected are disconnected by hand. Pulling a deep fryer away from a wall for cleaning or other purposes can break the hose connections without disconnecting the coupling members, enabling natural gas to spill out and possibly to ignite.
Other quick-disconnect couplings can be pulled apart by applying opposing separating forces on the coupling members, such as by pulling on an appliance hose where the coupling member on the supply side to the appliance is rigidly mounted. However, many restaurant employees are accustomed to disconnecting the quick-disconnect devices by hand and may not realize under stress that a particular coupling can be disconnected by pulling on the fuel hose or appliance, but may not be disconnectable through manual engagement.
The presence of a gas line through which gas is flowing in an area prone to frequent fires causes some concern beyond shutting off the supply of gas in the event that the appliance is disconnected from the fuel source. When a fire or other sudden heat rise condition occurs, then it is desirable to shut off the flow of gas whether or not the mating parts of the quick-disconnect device are separated. A danger exits that the fuel source could be ignited when the appliance and the fuel source are connected and fuel is flowing. The fuel could exacerbate an existing fire or result in an explosion.
Several patents describe various quick-disconnect devices for use in gas fuel supply lines for appliances such as deep fryers, space heaters, outdoor grills, and the like, that provide a means for shutting off the flow of gas fuel in the event of a fire or other sudden heat rise condition. For example, Gailey U.S. Pat. No. 4,825,893 relates to a coupling with a socket assembly that has a heat fusible element to enable a mating plug to be withdrawn from the socket assembly and gas flow to stop on exposure to excessive heat. The heat fusible portion of the retaining assembly can be the retaining element or the sleeve. When the fusible element is exposed to heat and fails, then the plug is ejected from the socket by a spring biased valve. The valve shuts off the flow of gas. In normal operation, the sleeve is axially retracted by hand to release the retaining elements for inserting the plug for coupling with the socket and for releasing the plug for withdrawal. Pull-to-disconnect features are not disclosed.
In the Gailey patent, the retaining elements can be retaining balls or retaining elements with a cylindrical or pin-shaped configuration. The heat fusible elements are made of a polymeric material sold under the trademark DELRIN.RTM. that loses its rigidity and is reduced to a plastic state when heated to a temperature in excess of 200.degree. F.
Typically, however, it is desirable to use steel for the retaining elements and brass, steel, or some other suitable metal for the sleeve. The retaining elements and sleeve are moving parts and can be subjected to a number of stresses. Use of plastic elements could adversely impact the useful life and operating characteristics of these couplings.
Snyder U.S. Pat. No. 3,532,101 discloses a gas coupling designed to connect a gas appliance to a source of gas under low pressure. A valve that shuts off the flow of gas from the gas supply is contained in a socket within a fixed housing. The mating plug includes an unmelted solder ring in an annular groove in the wall of the flow passageway. The solder ring causes the valve to move axially to the open position when the plug is inserted into the housing. In the event of a fire, the solder ring melts and permits the valve to close as a safety feature. However, the plug and socket remain in coaxial coupled relation and are not separated.
The coupling members described in the Snyder patent can be separated simply by pulling on the plug. However, the retaining element is a coiled spring that is held in a coupling housing that is mounted in a standard electrical box and is not operable by hand for insertion of the plug into the socket or release of the plug from the socket. Typically, couplings used with gas appliances are ball detent couplings, which may provide a more secure coupling engagement.
Hansen et al. U.S. Pat. No. 3,245,423 relates to a ball detent coupling having a fusible material for closing the valve on the supply side of the coupling in the event of a fire or excessive heat. The fusible material is located in the fluid passageway. In one embodiment, a nose member is mounted in the flow passageway of the plug by a band of solder. The nose member opens a spring biased valve when the plug and socket are connected. When the solder fuses, the nose member moves in response to the spring biased valve and allows the valve to close. The socket and plug remain locked in coaxial coupling relation. Manufacture of such a coupling requires extra steps to insert the nose member into the plug fluid passageway and to solder the nose member in place. Also, the plug and socket are connected and disconnected by retracting the sleeve by hand to insert or withdraw the plug. Pull-to-disconnect features are not disclosed.
Hansen Coupling Division of Tuthill Corporation in Cleveland, Ohio presently sells couplings under the trademark GAS-MATE.RTM. that are somewhat similar to that described in U.S. Pat. No. 3,245,423. One such coupling has two sets of radially extending ball detents circumscribing the socket. The two sets of detents are not in the same plane through the socket. In addition to the step of inserting the nose member into the plug and fixing it in place, two separate sets of ball retaining apertures are drilled in the socket to accommodate the two sets of detents. The result is a push-to-connect coupling with a heat responsive feature for stopping gas flow. However, the coupling elements remain connected in the event of a fire. Also, the coupling is disconnected by manual engagement by retracting the ball retaining sleeve by hand, and is not disconnectable by applying opposing separating forces on the socket and plug. A restaurant employee or fireman could not move a deep fryer away from a wall or out of a particular area without either taking time to operate the quick-disconnect device by hand or otherwise breaking the hose connections, even where the gas flow has been shut off.
Norton U.S. Pat. No. 4,280,523 discloses a coupling in which the plug body carries a collar for engaging the retaining balls in the socket. The collar is held in place on the plug by a temperature responsive annular fusible body of a material such as solder. When the temperature responsive body is melted, the collar and plug are disengaged and the plug is ejected from the socket. The collar remains in the socket. The device described in the Norton patent is disconnected normally by retracting the sleeve, and involves additional parts for the plug.
Thus, available quick-disconnect devices for gas fuel generally do not address all of the problems that can arise in the manufacture and use of such devices. While individual solutions have been proposed for specific problems, other problems are either not addressed or arise as a direct result of the proposed solution.